Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

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Electronic structure investigations of 4-aminophthal hydrazide by UV–visible, NMR spectral studies and HOMO–LUMO analysis by ab initio and DFT calculations K. Sambathkumar a,⇑, S. Jeyavijayan b, M. Arivazhagan c a b c

P.G.&Research Department of Physics, A.A. Govt. Arts College, Villupuram 605602, India Department of Physics, J.J. College of Engineering and Technology,Tiruchirappalli 620 009, India Department of Physics, Government Arts College, Tiruchirappalli 620 022, India

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 The APH was characterized by FT-IR,

FT-Raman, NMR and UV spectroscopy.  Quantum chemical calculations were done by DFT method.  The global minimum energy between the two methods shows the difference in optimizations.  The TED calculation provides a strong support for the frequency assignment.  HOMO, LUMO energies and MEP distribution of APH were performed.

Lumo energy= -0.1781a.u.

ΔE=-0.1058

Homo energy=-0.2839a.u

a r t i c l e

i n f o

Article history: Received 14 October 2014 Received in revised form 9 February 2015 Accepted 1 March 2015 Available online 24 March 2015 Keywords: FTIR FT-Raman HOMO-LUMO NMR UV MEP

a b s t r a c t Combined experimental and theoretical studies were conducted on the molecular structure and vibrational spectra of 4-AminoPhthalhydrazide (APH). The FT-IR and FT-Raman spectra of APH were recorded in the solid phase. The molecular geometry and vibrational frequencies of APH in the ground state have been calculated by using the ab initio HF (Hartree–Fock) and density functional methods (B3LYP) invoking 6-311+G(d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF and B3LYP method show best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of APH with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled Hartree–Fock approach for molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamentals is very small. A detailed interpretation of the NMR spectra of APH was also reported. The theoretical spectrograms for infrared and Raman spectra of the title molecule have been constructed. UV–vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time dependent density functional theory (TD-DFT) approach. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra. And the temperature dependence of the thermodynamic properties of constant pressure (Cp), entropy (S) and enthalpy change (DH0 ? T) for APH were also determined. Ó 2015 Elsevier B.V. All rights reserved.

⇑ Corresponding author. Tel.: +91 9994188861. E-mail address: [email protected] (K. Sambathkumar). http://dx.doi.org/10.1016/j.saa.2015.03.012 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

Introduction Hydrazides and hydrazones, the acylated derivatives [1] of hydrazine besides being useful for a number of biological properties, hydrazides are important starting material for a wide range of derivatives utilizable in pharmaceutical products and as surfactants. The hydrazones derivatives are used for fungicides, and in the treatment such as tuberculosis, leprosy and mental disorders. Biological assessment of fatty hydrazide and the derivatives have been the focus of earlier investigative studies [2,3]. The fatty hrdrazides are further derivatives to obtain new anti bacterial and anti fungal agents. Acylhydrazones, as an example of Schiff bases, and their metal complexes have widely studied due to their versatile applications in the fields of analytical and medicinal chemistry and biotechnology [4–6]. p-Hydroxy benzohydrazide moiety and its analogs seemed to be suitable parent compounds upon which variety of biological activities are reported such as antitumor [7,8], antianginal [9], antitubercular [10], antihypertensive [11] and antibacterial [12]. Hydrazides have recently become attractive to theoreticians as well as experimentalists due to the biological significance particularly in medicinal and enzyme chemistry. Harmonic force fields of polyatomic molecule play a vital role in the interpretation of vibrational spectra and in the prediction of other vibrational properties. Many substituted hydrazides are employed in the treatment of psychotic and psychoneurotic conditions. Carboxylic acid hydrazides are known to exhibit strong antibacterial activities which are enhanced by complexation with metal ions. The vibrational spectral studies of hydrazone is analyzed by Durig et al. [13]. The FTIR and FT-Raman spectra of 4-AminoPhthalohydrazide, and carried out normal coordinate calculations using classical method developed by Wilson to support the vibrational analysis [14]. To our knowledge, literature survey also reveals that to the best of our knowledge no theoretical calculations or detailed vibrational infrared and Raman analysis have been performed on APH molecule so far. A systematic study on the vibrational spectra and structure will aid in understanding the vibrational modes of this title molecule. So, in this work, the vibrational wave numbers, geometrical parameters, modes of vibrations, minimum energy, 1H and 13C NMR chemical shifts are calculated with GIAO approach by applying B3LYP method and electrostatic potential also provide information about electronic effects of APH molecule were investigated by using ab initio HF and B3LYP calculations with 6-311+G(d,p) basis set. And the electronic dipole moment (l) and the first hyperpolarizability (b) value of the investigate molecule computed show that the APH molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. The UV spectroscopic studies along with HOMO, LUMO analysis have been used to elucidate information regarding charge transfer within the molecule. The temperature dependence of the thermodynamic functions and their correlations were performed. Synthesis procedure of 4-AminoPhthalhydrazide In this experiment the chemiluminescent compound luminol, or 4-AminoPhthalhydrazide, will be synthesized from 4-nitrophthalic acid. It was performed by adding 10 g phthalimidehydrate in 20 ml water to a suspension of 4-nitrophthalimide (38.4 g0 ) of 4-nitrophthalimide in 250 ml water and refluxing for an hour. When this solution is acidified with acetic acid a pale yellow crystalline product is collected with suction on cooling. Purification was accomplished with solution in 3 L boiling 50% acetic acid, rapid filtration, followed by cooling and collection of pale yellow product. The melting point of 4-AminoPhthalhydrazide 299– 300 °C. The calculated (found) % for C8H7N3O2: C, 54.24 (53.24); H, 3.98(3.95); N, 23.72 (22.71) and O, 18.06 (17.04). The first step

125

of the synthesis in the simple formation of cyclic diamide, 4-nitrophthalhydrazide by reaction of 4-nitrophthalic acid with hydrazine.

In the second step 4-nitrophthalhydrazide back to the large side-arm test tube. Add 6.5 ml of a 10% sodium hydroxide solution, and stir the mixture until the hydrazide dissolves. Add 4 g of sodium dithionite (sodium hydrosulfite). Using a pipet, add about 10 ml of water to wash the solid from the walls of the test tube. Heat the test tube with a micro burner until the solution boils. Stir the solution with a long glass rod. Maintain the boiling, with stirring, for 5 min. Add 2.6 ml of glacial acetic acid. Cool the test tube to room temperature. Stir the mixture during this cooling step. Finally, cool the solution in an ice bath. Collect the crystals of luminal by vacuum filtration using a Hirsch funnel.

The reliability of the results of normal coordinate analysis depends on the availability of spectral data like frequencies. For a large number of molecules, this data may not be available. Spectral data of high precision can be obtained for the sample using the sophisticated spectroscopic equipments with the advent of powerful monochromatic laser source and photoelectric recording in both Raman and infrared instruments, quality spectral can be recorded in a short interval of time. All the chemical purchased from Lancaster chemical company, U.K. and used as such without any further purification. Fourier transform infrared (FTIR) spectrum of the title molecule is recorded in the range of 4000–400 cm1 at a resolution of ±cm1 using a BRUKER IFS 66V FTIR spectrophotometer equipped with a cooled MCT detector. Boxcar apodization was used for the 250 averaged interferograms collected for both the samples and background. The FT-Raman spectrum is recorded on a computer interfaced BRUKER IFS model interferometer, equipped with FRA 106 FT-Raman accessory in the 3500–50 cm1 stokes region, using the 1064 nm line of Nd:YAG laser for excitation operating at 200 mW power. The reported wave numbers are believed to be accurate within ±1 cm1. The UV–visible absorption spectra of APH are examined in the range 200–500 nm using SHIMADZU UV-1650 PC, UV–vis recording spectrometer. The UV pattern is taken from 105 molar solution of APH, solved in ethanol. Computational details Density functional theory calculations are carried out for APH, Hartree–Fock (HF) and DFT calculations using GAUSSIAN 09W program package [15]. Initial geometry generated from the standard geometrical parameters was minimized without any constraint on the potential energy surface at Hartree–Fock level adopting the standard 6-311+G(d,p) basis set. This geometry was then re-optimized again at DFT level employing the B3LYP keyword, which invokes Becke’s threeparameter hybrid method [16] using the correlation function of Lee et al. [17], implemented with the same basis set for better

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description of the bonding properties of amino group. All the parameters were allowed to relax and all the calculations converged to an optimized geometry which corresponds to a true minimum, as revealed by the lack of imaginary values in the wave number calculations. The Cartesian representation of the theoretical force constants have been computed at the fully optimized geometry. The multiple scaling of the force constants were performed according to SQM procedure [18] using selective scaling in the natural internal coordinate representation [19]. Transformation of force field, the subsequent normal coordinate analysis including the least square refinement of the scale factors and calculation of the total energy distribution (TED) were done on a PC with the MOLVIB program (version V7.0-G77) written by Sundius [20,21]. The systematic comparison of the results from DFT theory with results of experiments has shown that the method using B3LYP functional is the most promising in providing correct vibrational wave numbers. The calculated geometrical parameters were compared with X-ray diffraction result [22]. Normal coordinate analyses were carried out for the title compound to provide a complete assignment of fundamental frequencies. For this purpose, the full set of 77 standard internal coordinates (containing 23 redundancies) for APH was defined as given in Table 1. From these, a non-redundant set of local symmetry coordinates were constructed by suitable linear combinations of internal coordinates following the recommendations of Fogarasi et al. [19] is summarized in Table 2. The theoretically calculated force fields were transformed to this set of vibrational coordinates and used in all subsequent calculations.

Table 2 Definition of local symmetry coordinates of 4-AminoPhthalhydrazide.

Prediction of Raman intensities The Raman activities (Si) calculated with the GAUSSIAN 09W program are subsequently converted to relative Raman intensities

a

No. (i)

Type

Definitiona

1–3 4–11 12 13–15 16, 17 18, 19 20

CH CC NN NC NH CO NH2ss

R1, R2, R3 r4, r5, r6, r7, r8, r9, r10, r11 S12 q13, q14, q15 p16, p17 X18, X19 pffiffiffi (Q20 + Q21)/ 2 pffiffiffi (Q20  Q21)/ 2

21

NH2ips

22

R1trigd

23

R1symd

24

R1asymd

25

R2trigd

26

R2symd

27

R2asymd

28–30

bCH

31

b NH

32

b NN

33, 34

b CO

35, 36

b CN

37, 38

b NH

39–41 42–44 45, 46 47

xCH x NH x CO Ring trigd

48

Ring symd

49

Ring asymd

50

Ring trigd

51

Ring symd

pffiffiffi (a22  a23 + a24  a25 + a26  a27)/ 6

pffiffiffiffiffiffi (a22  a23 + 2a24  a25  a26  2a27)/ 12 pffiffiffi (a22  a23 + a25  a26)/ 2 pffiffiffi (a28  a29 + a30  a31 + a32  a33)/ 6 pffiffiffiffiffiffi (a28  a29 + 2a30  a31  a32  2a33)/ 12 pffiffiffi (a28  a29 + a31  a32)/ 2 pffiffiffi pffiffiffi pffiffiffi (b34  b35)/ 2, (b36  b37)/ 2, (b38  b39)/ 2 pffiffiffi pffiffiffi b40  b41/ 2, g42  g43/ 2 pffiffiffi g42  g43/ 2 pffiffiffi pffiffiffi (Z44  Z45)/ 2, (L46  L47)/ 2 pffiffiffi pffiffiffi X48  X49/ 2, M50  M51/ 2 pffiffiffi T52, (d53  d54)/ 2 w55, w56, w57 q58, q59, q60

v61, v62

pffiffiffi (s63  s64 + s65  s66 + s67  s68)/ 6 pffiffiffi (s63  s65 + s66  s68)/ 2

52

Ring asymd

pffiffiffiffiffiffi (s63 + 2s64  s65  s66 + 2s67  s68)/ 12 pffiffiffi (s69  s70 + s71  s72 + s73  s74)/ 6 pffiffiffi (s69  s71 + s72  s73)/ 2 pffiffiffiffiffiffi (s69 + 2s70  s71  s72 + 2s73  s74)/ 12

53 54

t C-NH2 Butterfly

pffiffiffi (s76  s77)/ 2

s75

The internal coordinates used here are defined in Table 1.

Table 1 Definition of internal coordinates of 4-AminoPhthalhydrazide.

a

No. (i)

Symbol

Type

Definitiona

Stretching 1–3 4–11 12 13–15 16–17 18, 19 20, 21

Ri ri Si qi Pi xi Qi

C–H C–C N–N N–C N–H C–O NH2

C3–H14, C5–H20, C6–H19 C1–C2, C2–C3, C3–C4,C4–C5, C5–C6, C6–C1,C1–C7, C2–C10 N8–N9 N8–C7, N9–C10, N11–C4 N8–H16, N9–H17 C7–O18, C10–O15 N11–H12, N12–H13

ai ai

C1–C2–C3, C2–C3–C4, C3–C4–C5, C4–C5–C6, C5–C6–C1, C6–C1–C2 C7–N8–N9, N8–N9–C10, N9–C10–C2, C10–C2–C1, C2–C1–C7, C1–C7–N8 C1–C6–H19, C5–C6–H19, C6–C5–H20, C4–C5–H20, C2–C3–H14, C4–C3–H11 C7–N8–H17, C10–N9–H16 N9–N8–H17, N8–N9–H16 C1–C7–O18, C2–C10–O15 N8–C7–O18, N9–C10–O15 C3–C4–N11, C5–C4–N11 C4–N11–H12, C4–N11–H12 H12–N11–H13 N9–N8–H17, N8–N9–H16

In-plane bending 22–27 28–33 34–39 40, 41 42, 43 44, 45 46, 47 48, 49 50–51 52 53, 54

bi bi gi Zi Li Xi Mi Ti di

Ring1 Ring2 C–C–H C–N–H N–N–H C–C–O N–C–O C–C–N C–N–H H–N–H N–N–H

Out-of-plane bending 55–57 58–60 61, 62

wi qi vi

C–H H–N C–O

H14–C3–C2–C4, H19–C6–C5–C1, H20–C5–C6–C4 H16–N9–C10–N8, H17–N8–N9–C7, C4–N11–H12–H13 O15–C10–N9–C2, O18–C7–N8–C1

Torsion 63–68 69–74 75 76, 77

si si si si

t Ring t Ring t C-NH2 Butterfly

C1–C2–C3–C4, C2–C3–C4–C5, C3–C4–C5–C6, C4–C5–C6–C1, C5–C6 –C1–C2, C6–C1–C2–C3 C7–C8–C9–C10, C8–C9–C10–C2, C9–C10–C2–C1, C10–C2–C1–C7, C2–C1–C7–C8, C1–C7–C8–C9 C4–N11–H12–H13 C6–C1–C2–C10, C7–C1–C2–C3

For numbering of atoms refer Fig. 1.

K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

(Ii) using the following relationship derived from the basic theory of Raman scattering [23]

Ii ¼

f ðm0  v i Þ4 Si h i v i 1  exp hckTmi

where m0 is the exciting frequency in cm1, mi the vibrational wave number of the ith normal mode, h, c and k are the fundamental constants and f is a suitably chosen common normalization factor for all the peak intensities. Results and discussion Molecular geometry The optimized molecular structure of APH along with numbering of atoms is shown in Fig. 1. The optimized structure parameters of APH obtained by DFT-B3LYP/6-311+G(d,p) and HF/6-311+G(d,p) levels are listed in Table 3. From the structural data given in Table 3, it is observed that the various bond lengths are found to be almost same at HF/6-311+G(d,p) level of theory, in general slightly over estimates bond lengths but it yields bond angles in excellent agreement with the HF method. The calculated geometric parameters can be used as foundation to calculate the other parameters for the compound. The optimized molecular structure of APH reveals that the N-heterocyclic rings of amino group are in planar. Inclusion of CH group and NH atoms known for its strong electron-withdrawing nature, in heterocyclic position, is expected to increase a contribution of the resonance structure, in which the electronic charge is concentrated at this site. This is the reason for the shortening of bond lengths N11–H12 = 0.994 Å and N11– H13 = 0.995 Å obtained by HF method. The same bond lengths calculated by DFT method is found to be 1.009 Å and 1.010 Å. The carbon atoms are bonded to the hydrogen atoms with an r-bond in heterocyclic ring and the substitution of hydrogen atoms for hydrogen reduces the electron density at the ring carbon atom. In APH, the N–H bond lengths vary from 0.997 Å to 0.999 by HF method and from 1.013 to 1.014 B3LYP methods. The ring carbon atoms in substituted heterocyclic exert a larger attraction on the valence electron cloud of the hydrogen atom resulting in an increase in the C–H force constants and a decrease in the corresponding bond length. It is evident from the C–C bond lengths ranging from 1.375 Å to 1.489 Å by HF method and from 1.385 to 1.485 by B3LYP method in the heterocyclic rings of APH, whereas the C–H bond lengths in APH vary from 1.073 Å to1.076 Å and from

1.084 to 1.086 Å by HF and B3LYP methods, respectively. The heterocyclic rings appear to be a little distorted because of the NH2 group substitution as seen from the bond angles C3–C4–C5 which are calculated as 118.96° and 118.76° respectively, by HF and B3LYP methods and they are smaller than typical hexagonal angle of 120°. The comparative graphs of bond lengths, bond angles and dihedral angles of APH for three sets are presented in Figs. 2–4 respectively. From the theoretical values, it is found that most of the optimized bond lengths are slightly larger than the experimental values, due to that the theoretical calculations belong to isolated molecules in solid phase and the experimental results belongs to molecules in solid state.

First hyperpolarizability The potential application of the title compound in the field of nonlinear optics demands, the investigation of its structural and bonding features contribution to the hyperpolarizability enhancement, by analyzing the vibrational modes using IR and Raman spectroscopy. Many organic molecules, containing conjugated p electrons are characterized by large values of molecular first hyper polarizabilities, were analyzed by means of vibration spectroscopy [24]. In most of the cases, even in the absence of inversion symmetry, the strongest band in the IR spectrum is weak in the Raman spectrum and vice versa. But the intramolecular charge from the donor to acceptor group through a p-bond conjugated path can induce large variations of both the molecular dipole moment and the molecular polarizability, making IR and Raman activity strong at the same time. The experimental spectroscopic behavior described above is well accounted for a calculations in p conjugated systems that predict exceptionally infrared intensities for the same normal modes. The first hyperpolarizability (b) of this novel molecular system is calculated using the ab initio quantum mechanical method, based on the finite-field approach. In the presence of an applied electric field, the energy of a system is a function of the electric field. The first hyperpolarizability is a third-rank tensor that can be described by a 3  3  3 matrix. The 27 components of the 3D matrix can be reduced to 10 components due to the Kleinman symmetry [25]. The components of b are defined as the coefficients in the Taylor series expansion of the energy in the external electric field. When the electrical field is weak and homogeneous, this expansion becomes

E ¼ E0 

X

li F i 

i

Fig. 1. Molecular structure of 4-AminoPhthalhydrazide.

127

1X 1X 1 X aij F i F j  bijk F i F j F k  mijkl F i F j F k F l 2 ij 6 ijk 24 ijkl

where E0 is the energy of the unperturbed molecule; Fi is the field at the origin; and li, aij, bijk and cijkl and are the components of dipole moment, polarizability, the first hyperpolarizabilities and second hyperpolarizabilities, respectively. The calculated total dipole moment (l) and mean first hyperpolarizability (b) of APH are 1.1437 Debye and 8.3541  1030 esu, respectively, which is comparable with the reported values of similar derivatives. The large value of hyperpolarizibilities, b which is a measure of the non-linear optical activity of the molecular system, is associated with the intramolecular charge transfer, resulting from the electron cloud movement through p conjugated frame work from electron donor to electron acceptor groups. The physical properties of these conjugated molecules are governed by the high degree of electronic charge delocalization along the charge transfer axis and by the low band gaps. So we conclude that the title compound is an attractive object for future studies of nonlinear optical properties.

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Table 3 Optimized geometrical parameters of 4-AminoPhthalhydrazide obtained by HF/6-31+G(d,p) and B3LYP/6-311G+(d,p) density functional theory calculations. Bond length

C1–C2 C1–C6 C1–C7 C2–C3 C2–C10 C3–C4 C3–H14 C4–C5 C4–N11 C5–C6 C5–H20 C6–H19 C7–N8 C7–O18 N8–N9 N8–H17 N9–C10 N9–H16 C10–O15 N11–H12 N11–H13

Value (Å) HF/6-311+G(d,p)

B3LYP/6-311+G(d,p)

1.387 1.391 1.474 1.382 1.489 1.392 1.074 1.402 1.379 1.375 1.076 1.073 1.371 1.201 1.401 0.999 1.363 0.997 1.199 0.994 0.995

1.408 1.403 1.472 1.393 1.485 1.404 1.085 1.415 1.381 1.385 1.086 1.084 1.387 1.229 1.411 1.014 1.378 1.013 1.229 1.009 1.010

Dihedral angle

C6–C1–C2–C3 C6–C1–C2–C10 C7–C1–C2–C3 C7–C1–C2–C10 C2–C1–C6–C5 C2–C1–C6–H19 C7–C1–C6–C5 C7–C1–C6–H19 C2–C1–C7–N8 C2–C1–C7–O18 C6–C1–C7–N8 C6–C1–C7–O18 C1–C2–C3–C4 C1–C2–C3–H14 C10–C2–C3–C4 C10–C2–C3–H14 C1–C2–C10–N9 C1–C2–C10–O15 C3–C2–C10–N9 C3–C2–C10–O15 C2–C3–C4–C5 C2–C3–C4–N11 H14–C3–C4–C5 H14–C3–C4–N11 C3–C4–C5–C6

Expa

Bond angle

Value (°) HF/6-311+G(d,p)

B3LYP/6-311+G(d,p)

1.359 1.383

C2–C1–C6 C2–C1–C7 C6–C1–C7 C1–C2–C3 C1–C2–C10 C3–C2–C10 C2–C3–C4 C2–C3–H14 C4–C3–H14 C3–C4–C5 C3–C4–N11 C5–C4–N11 C4–C5–C6 C4–C5–H20 C6–C5–H20 C1–C6–C5 C1–C6–H19 C5–C6–H19 C1–C7–N8 C1–C7–O18 N8–C7–O18 C7–N8–N9 C7–N8–H17 N9–N8–H17 N8–N9–C10

118.96 120.94 120.12 121.22 119.81 118.93 119.82 119.05 121.11 118.96 120.66 120.33 120.72 119.41 119.85 120.34 118.92 120.73 116.00 124.04 119.95 121.61 112.55 111.85 122.47

118.78 121.27 119.91 120.88 120.41 118.67 120.21 118.47 121.30 118.76 120.74 120.45 120.77 119.34 119.88 120.56 118.47 120.96 115.41 125.00 119.57 122.02 113.73 113.08 122.95

1.415 1.423 0.917 1.391 1.347 1.364 0.884 0.920

0.872 1.460 1.405 0.908 0.887

Expa

120.3 121.7 119.8 121.6

116.4

121.1 122.5 119.8 119.6 121.7

120.3 123.3

119.8 115.2

Expa

Value (°) HF/6-311+G(d,p)

B3LYP/6-311+G(d,p)

0.7074 179.01 178.77 2.916 0.5978 179.40 178.68 1.314 7.242 173.28 174.71 4.757 0.436 179.78 178.75 1.465 7.406 173.11 174.24 5.230 0.049 177.64 179.82 2.1264 0.052

0.733 178.91 178.84 2.972 0.5812 179.50 178.72 1.3642 6.9752 173.70 174.93 4.3905 0.539 179.63 178.75 1.4214 6.485 174.06 175.29 4.158 0.182 177.54 179.99 2.276 0.0336

For numbering of atoms refer Fig. 1. a Value taken from Ref. [22].

NMR spectral analysis The isotropic chemical shifts are frequently used as an aid in identification of reactive organic as well as ionic species. It is recognized that accurate predictions of molecular geometries are essential for reliable calculations of magnetic properties. Therefore, full geometry optimization of APH were performed by using B3LYP/6-311+G(d,p) method. Then, Gauge-Including Atomic Orbital (GIAO) 1H and 13C chemical shift calculations of the compound has been made by same method. Application of the GIAO [26] approach to molecular systems was significantly improved by an efficient application of the method to the ab initio SCF calculations, using techniques borrowed from analytic derivative methodologies. GIAO procedure is somewhat superior

since it exhibits a faster convergence of the calculated properties upon extension of the basis set used. Taking into account the computational cost and the effectiveness of calculation, the GIAO method seems to be preferable from many aspects at the present state of this subject. On the other hand, the density functional methodologies offer an effective alternative to the conventional correlated methods, due to their significantly lower computational cost. The molecular structure of APH is optimized by B3LYP method with 6-311+G(d,p). Then, gauge-including atomic orbital (GIAO) 13C and 1H chemical shift calculation of title compound is made by using B3LYP method. The 1H and 13C chemical shifts were measured in a less polar (CDCl3) solvent. The result in Table 4 shows that the range 13C NMR chemical shift of the typical organic molecule usually is >100 ppm [27,28], the accuracy ensures

K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

HF/6-311+G(d,p) B3LYP/6-311+(d,p) 1.5

1.4

Value(A0)

1.3

1.2

1.1

C1-C2 C1-C6 C1-C7 C2-C3 C2-C10 C3-C4 C3-H14 C4-C5 C4-N11 C5-C6 C5-H20 C6-H19 C7-N8 C7-O18 N8-N9 N8-H17 N9-C10 N9-H16 C10-O15 N11-H12 N11-H13 ----Fig. 2. Bond length differences between theoretical (HF and DFT) approaches.

reliable interpretation of spectroscopic parameters. It is true from the above literature value, in our present study, the title molecule also falls with the above literature data except with the carbon atoms (C4). In the present paper, the signal observed at 190.30 ppm in 13C NMR spectrum is assigned to C10 carbon atom correlates with theoretically predicted value at 187.473 ppm. The signals for aromatic carbons were observed at 127.70– 184.70 ppm in 13C NMR spectrum for the title molecule, since those carbon atoms which belong to APH also exactly correlate with theoretically predicted value at 131.096–186.714 ppm. The signals of the aromatic proton were observed at 21.01– 23.20 ppm. The calculated proton NMR chemical shifts show moderate agreement with the experimental values except with aliphatic proton H16, H17. The H atom is the smallest of all atoms and

HF/6-311+G(d,p) B3LYP/6-311+G(d,p)

122 120 0

This electronic absorption correspond to the transition from the ground to the first excited state and is mainly described by one electron excitation from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) [30,31]. The HOMO is located over nitrogen and hydrogen group and the HOMO–LUMO transition implies an electron density transfer to the oxygen group from heterocyclic ring to nitrogen group. Moreover, these orbital’s significantly overlap in their position for APH. The HOMO–LUMO energy gap of APH was calculated at B3LYP level, which reveals that the energy gap reflects the chemical activity of molecule. The LUMO as an electron acceptor (EA) represents the ability to obtain an electron (ED) and HOMO represents ability to donate an electron (ED). The ED groups to the efficient EA groups through p-conjugated path. The strong charge transfer interaction through p-conjugated bridge results in substantial ground state Donor–Acceptor (DA) mixing and the appearance of a charge transfer band in the electron absorption spectrum. The atomic orbital compositions of the frontier molecular orbital and few MOs are sketched in Fig. 6. The calculated self-consistent field (SCF) energy of APH is – 623.9537 a.u. The HOMO and LUMO energy gap explains the fact that eventual charge transfer interaction is taking place within the molecule. Global and local reactivity descriptors Based on density functional descriptors global chemical reactivity descriptors of molecules such as hardness, chemical potential, softness, electronegativity and electrophilicity index as well as local reactivity have been defined [32–36]. Pauling introduced the concept of electronegativity as the power of an atom in a molecule to attract electrons to it. Hardness (g), chemical potential (l) and electronegativity (v) and softness are defined follows.

124

Value( )

mostly localized on the periphery of molecules. Therefore their chemical shifts would be more susceptible to intermolecular interactions in the aqueous solution as compared to that for other heavier atoms. Another important aspect is that, hydrogen attached or nearby electron with drawing atom or group can decrease the shielding and moves the resonance of attached proton towards to a higher frequency. By contrast electron donating atom or group increases the shielding and moves the resonance towards to a lower frequency. In this study, the chemical shifts obtained and calculated for the hydrogen atoms of amino groups are high. All values are [29] due to shielding effect. It is true from above literature data in our present study the amino protons at N11 appears as singlet with two proton integral at 27.40–27.41 ppm shows good agreement with computed chemical shift values are shown in Table 4. The relationship between the experimental chemical shift and computed chemical shift GIAO/B3LYP/6311+G(d,p) levels for 13C are shown in Fig. 5. HOMO–LUMO analysis

1.0

126

129

118

g ¼ 1=2ð@2E=@N2ÞVðrÞ ¼ 1=2ð@ l=@NÞVðrÞ

116

l ¼ ð@E=@NÞVðrÞ

114

v ¼ l ¼ ð@E=@NÞVðrÞ

112

where E and V(r) are electronic energy and external potential of an N-electron system respectively. Softness is a property of molecule that measures the extent of chemical reactivity. It is the reciprocal of hardness:

C2-C1-C6 C2-C1-C7 C6-C1-C7 C1-C2-C3 C1-C2-C10 C3-C2-C10 C2-C3-C4 C2-C3-H14 C4-C3-H14 C3-C4-C5 C3-C4-N11 C5-C4-N11 C4-C5-C6 C4-C5-H20 C6-C5-H20 C1-C6-C5 C1-C6-H19 C5-C6-H19 C1-C7-N8 C1-C7-O18 N8-C7-O18 C7-N8-N9 C7-N8-H17 N9-N8-H17 N8-N9-C10 ---

110

Fig. 3. Bond angle differences between theoretical (HF and DFT) approaches.

S ¼ 1=g Using Koopmans’s theorem for closed-shell molecules, g, l and

v can be defined as

130

K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

HF/6-311+G(d,p) B3LYP/6-311+G(d,p) 200 150 100

0

Value( )

50 0 -50 -100 -150

--

--

C3-C4-C5-C6

H14-C3-C4-C5

H14-C3-C4-N11

C2-C3-C4-C5

C2-C3-C4-N11

C3-C2-C10-N9

C3-C2-C10-O15

C1-C2-C10-N9

C1-C2-C10-O15

C10-C2-C3-C4

C10-C2-C3-H14

C1-C2-C3-C4

C1-C2-C3-H14

C6-C1-C7-N8

C6-C1-C7-O18

C2-C1-C7-N8

C2-C1-C7-O18

C7-C1-C6-C5

C7-C1-C6-H19

C2-C1-C6-C5

C2-C1-C6-H19

C7-C1-C2-C3

C7-C1-C2-C10

C6-C1-C2-C3

C6-C1-C2-C10

-200

Fig. 4. Dihedral angle differences between theoretical (HF and DFT) approaches.

Table 4 Experimental and theoretical chemical shifts (13C, 1H) of 4-AminoPhthalhydrazide by B3LYP/6-311+G(d,p) method (ppm)]. Atom position

C1 C2 C3 C4 C5 C6 C7 N8 N9 C10 N11 H12 H13 H14 O15 H16 H17 O18 H19 H20

B3LYP Expt

6-311+G(d,p

65.90 63.41 127.70 153.56 130.80 131.01 184.70

114.474 18.0531 131.096 155.568 134.833 134.19 186.714 110.43 108.92 187.473 198.238 30.606 30.418 24.056 211.405 24.950 25.037 197.021 24.115 25.459

190.30 27.40 27.41 21.01 21.90 22.03 21.10 23.20

g ¼ ðI  AÞ=2

l ¼ ðI þ AÞ=2

v ¼ ðI þ AÞ=2 where A and I are the ionization potential and electron affinity of the molecules respectively. The ionization energy and electron affinity can be expressed through HOMO and LUMO orbital energies as I = EHOMO and A = ELUMO. Electron affinity refers to the capability of a ligand to accept precisely one electron from a donor. However in many kinds of bonding viz covalent hydrogen bonding, partial charge transfer takes places. Recently Parr et al. [32] have defined a new descriptor to quantify the global electrophilic power of the molecule as electrophilicity index (x), which defines a quantitative classification of the global electrophilic nature of a molecule Parr et al. [32] have proposed electrophilicity index (x)

as a measure of energy lowering due to maximal electron flow between donor and acceptor. They defined electrophilicity index (x) as follows

x ¼ l2 =2g The usefulness of this new reactivity quantity has been recently demonstrated in understanding the toxicity of various pollutants in terms of their reactivity and site selectivity [37–39]. The calculated value of electrophilicity index describes the biological activity of APH. All the calculated values of hardness, potential, softness and electrophilicity index are shown in Table 5. UV-spectral analysis Ultraviolet spectra analysis of APH have been investigated by TD-DFT/B3LYP/6-311++G(d,p) method in ethanol. The calculated visible absorption maxima of kmax that are a function of the electron availability have been reported in Table 6. Calculations of molecular orbital geometry show that the visible absorption maxima of this molecule correspond to the electron transition between frontier orbitals such as translation from HOMO to LUMO. As can be seen from the UV–vis spectra absorption maxima values have been found to be 410, 348.8 and 312.08 nm. The kmax is a function of substitution, the stronger the donor character of the substitution, the more the electrons pushed into the molecule, the larger the kmax. These values may be slightly shifted by solvent effects. The role of substituents and of the solvent influences on the UVspectrum. The visible band observed around 343.71 nm could be attributed to high delocalization of p-electrons. These bands may be due to electronic transition of p ? p⁄. The calculated UV–vis spectrum is shown in Fig. 7. Vibrational spectra From the structural point of view the title compound is assumed to have C1 point group symmetry. The 54 fundamental modes of vibrations arising for APH are classified into 37A0 and 17A00 species. The A0 and A00 species represent the in-plane and out-of-plane vibrations, respectively. For visual comparison, the observed and calculated FTIR and FT-Raman spectra of APH at HF

K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138 200

160

140

120

13

Computed Cchemical shift(ppm)

180

100

80

60 C1

C2

C3

C4

C5

C6

C7

13

Experimental C chemical shift(ppm) Fig. 5. Comparative graph of experimental chemical shift and computed chemical shift of

Homo-4 energy=-0.3389 a.u.

13

C of NMR.

Lumo+4 energy= -0.0382 a.u.

Homo-3 energy=-0.3359 a.u.

Lumo+3 energy= -0.0670 a.u.

Homo-2 energy= -0.3351a.u.

Lumo+2 energy= -0.0887 a.u.

Homo-1 energy=-0.3243 a.u.

Lumo+1=-0.1707 a.u.

Homo energy=-0.2839a.u.

Lumo energy= -0.1781a.u.

Fig. 6. HOMO–LUMO plot of 4-AminoPhthalhydrazide.

131

132

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Table 5 HOMO–LUMO energy AminoPhthalhydrazide.

gap

and

related

molecular

properties

of

Molecular properties

B3LYP/6-311+G(d,p) (a.u.)

HOMO LUMO Energy gap Ionization potential (I) Electron affinity (A) Global softness (s) Global hardness (g ) Chemical potential (l) Global electrophilicity (x)

0.2839 0.1781 0.1058 0.2839 0.1781 18.9035 0.0529 0.231 0.5043

4-

and DFT/B3LYP level using 6-311+G(d,p) basis set are shown in Figs. 8 and 9, respectively. The detailed vibrational assignment of fundamental modes of APH along with the calculated IR and Raman frequencies and normal mode descriptions (characterize by TED) are reported in Table 7. Comparison of frequencies calculated at HF and B3LYP with experimental values revels the overestimation of the calculated vibrational modes due to neglect of harmonicity in real system. Inclusion of electrons correlation in DFT values smaller in comparison with the HF frequencies data. The calculated frequencies are slightly higher than the observed value for the majority of normal modes. The major factor which is responsible for these discrepancies between the experimental

Table 6 The computed excitation energies, oscillator strength, electronic transition configuration wavelength of 4-AminoPhthalhydrazide using TD-DFT/B3LYP/6-311+G(d,p). Excited state

EE (eV)

Oscillator strength f

Configuration

CI expansion coefficient

Wavelength (nm)

1

2.5419

0.0000

45 ? 48 46 ? 47 46 ? 47

0.10436 0.67862 0.67862

487.76

2

2.9139

0.0055

42 ? 47 45 ? 47 46 ? 48 42 ? 47 45 ? 48

0.19440 0.41471 0.44417 0.19440 0.19845

425.50

3

3.1891

0.0000

42 ? 48 45 ? 47 45 ? 48 46 ? 48 45 ? 47 45 ? 48 46 ? 48

0.13036 0.34885 0.30215 0.47218 0.34885 0.30215 0.47218

388.78

4

3.3644

0.1788

42 ? 48 43 ? 47 43 ? 48 44 ? 47 45 ? 47 45 ? 48 43 ? 48 44 ? 46 45 ? 48

0.16992 0.18248 0.14568 0.13277 0.40187 0.43448 0.14568 0.13277 0.43448

368.52

5

3.4654

0.0000

43 ? 47 43 ? 48 44 ? 47 44 ? 48 44 ? 47 44 ? 48

0.18827 0.18081 0.51423 0.36935 0.51423 0.36935

357.78

6

3.5005

0.0345

42 ? 47 43 ? 47 43 ? 48 43 ? 47 43 ? 48 44 ? 47 44 ? 48

0.10409 0.50595 0.27885 0.50595 0.27885 0.19475 0.19981

354.19

and computed value is related to the fact that the experimental value is an anharmonic frequency while the calculated value is harmonic frequency. While an harmonicity is the main factor of the discrepancies in the case of vibrations related to the NH2 and C@O bonds, for other vibrations most of the discrepancies come from the approximate nature of the used computational technique, and probably also from the lattice effects in the substance, studied as a solid. From the figure, it is found that the calculated (unscaled) frequencies by B3LYP with 6-311+G(d,p) basis sets are closer to the experimental frequencies than HF method with 6-311+G(d,p) basis set. This observation is supported by the literature report [24]. The standard deviation (SD) calculation made between experimental and computed frequencies (HF/DFT) for the APH is presented in Table 8. According to the SD, the computed frequency deviation decrease in going from HF/6-311+G(d,p) and B3LYP/6311+G(d,p). The deviation ratio between HF/6-311+G(d,p) and B3LYP/6-31+G(d,p) is 2.60. It also proved that, the calculated frequencies by B3LYP/6-311+G(d,p) basis sets are closer to the experimental frequencies than HF method.

C–H vibrations The hetero aromatic structure shows the presence of C–H stretching vibration in the region 3100–3000 cm1 which is the characteristic region for the ready identification of C–H stretching vibration [41]. In this region, the bands are not affected appreciably by the nature of substituents. The C–H stretching mode usually appears with strong Raman intensity and is highly polarized. In the FT-IR spectrum of APH, the weak bands at 3050, and 3000 cm1 are assigned to C–H stretching vibrations of hetro cyclic group. The counter part of the FT-Raman spectrum at 3015 cm1 is attributed to C–H stretching vibration. The theoretically computed wavenumber by B3LYP method falls in the range at 3052– 3001 cm1 are assigned to C–H stretching vibration as shown in Table 7. The TED corresponding to this vibration is a pure mode, and contributing of 97%. The C–H in-plane bending frequencies appear in the range 1000–1300 cm1 and are very useful for characterization purpose [42]. For our title molecule, the C–H inplane bending vibrations appear as a weak to weak bands in FTIR spectrum at 1198 and 1082 cm1 and 1200 and 1196 cm1 as a very weak to very weak band in FT-Raman spectrum shows good agreement with computed wavenumber by B3LYP/6-311+G(d,p) method at 1202–1084 cm1. The TED confirms these vibrations are mixed mode as it is evident from Table 7 almost contributing 40%. The C–H out-of-plane bending vibrations are strongly coupled vibrations and occur in the region 1000–750 cm1 [43]. The

Fig. 7. UV spectrum of 4-AminoPhthalhydrazide.

K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

133

Fig. 8. Comparison of observed and calculated IR spectra of 4-AminoPhthalhydrazide (a) observed in solid phase, (b) calculated with B3LYP/6-311+G(d,p) and calculated with HF/6-311+G(d,p).

aromatic C–H out-of-plane bending vibration of APH are assigned as medium strong band observed at 718 cm1 in FT-Raman and 735 and 729 cm1 as a medium strong to very weak bands in FTIR spectrum are well correlated with B3LYP/6-311+G(d,p) method at 738–719 cm1 with TED contribution of 30%. C@O vibrations The structural unit of C@O has an excellent group frequency, which is described as a stretching vibration. Since the C@O group is a terminal group, only the carbon is involved in a second

chemical bond this reduces the number of force constants determining the spectral position of the vibration. The C@O stretching vibration usually appears in a frequency range that relatively free of other vibrations. For example, in many carbonyl compounds the double bond of the C@O has a force constant different from those of such structural units such as C@C, C–C, C–H etc., only structural units of C@C have force constants of magnitudes similar to that of the C@O group. The C@C vibration could interact with C@O if it was the same species, but generally it is not. Almost all carbonyl compounds have a very intense and narrow peak in the range of 1800–1600 cm1 [44,45] or in other words the carbonyl

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K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

Fig. 9. Comparison of observed and calculated Raman spectra of 4-AminoPhthalhydrazide (a) observed in solid phase, (b) calculated with B3LYP/6-311+G(d,p) and calculated with HF/6-311+G(d,p).

stretching frequency has been most extensively studied by infrared spectroscopy [46]. The multiple bonded group is highly polar and therefore gives rise to an intense infrared absorption band in the region 1700–1800 cm1. The carbon–oxygen double bond is formed by Pp–Pp bonding between carbon and oxygen. Because of the different electro negativities of the carbon and oxygen atoms, the bonding electrons are not equally distributed between the two atoms. The following two resonance forms contribute to the bonding of the carbonyl group >C O ?C+–O. The lone pair of electrons on oxygen also determines nature of the carbonyl group [47]. In our present study, we can expect two C@O stretching vibration (i.e. C7@O18 and C10@O15), the conjugation of C10@O15 bond C7@O18 may increase its single bond character resulting in lowered values of carbonyl stretching wave numbers. The computed wave number by B3LYP/6-311+G(d,p) method at 1695 cm1 is assigned to C10@O15 stretching vibrations. The strong band in FT-Raman at 1693 cm1 is assigned to C10@C15 stretching mode. While in the case of C7@O18 stretching mode, the shoulder band in FT-IR spectrum at 1672 cm1 are in moderate agreement with computed wave number at 1674 cm1. The

lowering of wave number between the recorded as well as computed for C7@O18 stretch may be due to formation of intramolecular hydrogen bonding with adjacent CH moiety. N–H vibrations The hetero aromatic molecule containing an N–H group shows its stretching absorption in the region 3500–3220 cm1. This is usual range of appearance for NH2 vibrations. The position of absorption in this region depends upon the degree of hydrogen bonding, and hence upon the physical state of the sample or the polarity of the solvent [48]. The vibrational bands due to the N– H stretching are sharper and weaker than those of C–O stretching vibrations by virtue of which they can be easily identified [49]. The N–H stretching fundamental of piperidine was observed in the vapor phase at 3364 cm1. Gulluoglu et al. [50,51] observed in the liquid phase at 3340 cm1 for the N–H stretching of the piperidine. In our present study the very weak band observed in FT Raman spectrum at 3195 cm1 and broad band in FT-IR spectrum at 3245 and 3194 cm1 is assigned to N–H stretching vibration.

Table 7 The observed FT IR, FT-Raman and calculated (unscaled and scaled) frequencies (cm1), IR intensity (km mol1), Raman activity(A0 amu-1). and force constant (m dyne A0) and probable assignments(Characterized by TED) of 4AminoPhthalhydrazide using B3LYP/6-311+G(d,p) and HF/6-311+G(d,p) calculations. Symmetry species C1

0

Calculated frequencies (cm1) (unscaled)

Scaling frequency (cm1)

FT7-IR

FT-RAMAN

HF

B3LYP

HF

3352ms 3270ms 3245ms 3194w 3050w – 3000w – 1672vs – 1550ms 1492s – 1430s – 1382ms – – 1301ms – – – 1231w – – 1198w 1082w – – – 980w – 862vs – 790ms – 761w 753vw – 735ms 729vw – – 540w 501ms 491vw 428w – –

– 3272vw – 3195vw – 3015w – 1693s – 1610s 1550ms – 1488vs – 1410s – 1352ms 1324w – 1291w 1273vw 1250ms – 1212w 1200vw 1196vw – 1064w 1035vw 1010vw – 873w – 821s – 772s – – 749w – – 718ms 552w – – 491w 428vw 400ms 392vw

3936 3848 3845 3820 3394 3382 3350 1952 1925 1815 1786 1763 1677 1666 1615 1569 1558 1459 1401 1378 1356 1322 1301 1231 1210 1213 1113 1006 998 946 909 868 839 784 766 743 678 664 598 582 555 520 495 472 445 418 377 338 303

3714 3598 3596 3591 3219 3204 3182 1749 1734 1669 1650 1610 1537 1518 1495 1453 1399 1354 1338 1321 1317 1301 1278 1221 1180 1199 991 937 904 850 829 776 747 730 711 678 621 590 544 527 519 463 437 409 404 386 364 349 279

3399 3301 3288 3220 3090 3068 3044 1721 1710 1680 1590 1534 1520 1507 1488 1440 1399 1370 1322 1312 1301 1270 1255 1225 1239 1207 1110 1100 1070 1050 1010 899 880 856 810 790 777 763 759 748 741 723 600 589 530 521 500 489 432

Force constant (mDyne/A)

IR intensity (kM/mol)

Raman activity (A4/amu)

B3LYP

HF

B3LYP

HF

B3LYP

HF

B3LYP

3354 3271 3244 3195 3052 3014 3001 1695 1674 1611 1553 1494 1490 1431 1411 1384 1355 1326 1305 1294 1277 1254 1233 1214 1202 1197 1084 1067 1038 1013 985 877 864 822 794 773 764 755 749 738 730 719 557 544 505 495 432 402 395

10.052 9.4071 9.3941 9.0184 7.4329 7.3680 7.2184 20.850 20.013 2.4964 7.2776 13.452 3.2972 4.0608 4.8396 3.2983 3.4802 2.7202 4.7285 2.2849 2.9335 2.3498 1.3756 2.3978 1.4310 2.1246 0.9841 1.2751 1.3957 0.8417 2.1917 2.1683 3.1974 1.9269 1.1983 1.1804 1.3025 0.5072 0.8064 0.8124 0.3599 0.2482 0.6009 0.4085 0.4690 0.5452 0.6230 0.0702 0.2606

8.9572 7.9904 8.2166 8.1924 6.6759 6.5985 6.5022 16.761 15.296 2.5478 4.3733 11.117 4.5510 2.7173 3.8751 1.9633 8.0207 5.4908 2.4526 3.7188 1.5582 1.9457 1.0354 1.6275 1.8330 1.2839 0.7650 1.9805 0.7185 0.6717 1.9514 1.8759 2.5785 1.9104 1.2136 0.9684 1.1582 0.3997 0.6287 0.6568 0.3155 0.5885 0.3817 0.2595 0.1302 0.3722 0.0860 0.5172 0.2251

34.4492 91.4206 69.3341 61.4561 1.8532 3.3087 12.6096 40.3830 1038.22 277.74 173.891 13.9598 25.7765 2.7410 41.7697 143.211 384.315 46.741 79.773 98.3102 2.1129 32.3403 37.6325 36.4015 5.5271 36.2891 0.6080 8.9294 19.8925 30.5459 17.8447 26.0512 115.541 10.5929 16.0067 7.0684 11.4700 200.301 16.9937 19.4920 37.2770 435.88 44.4156 37.9667 24.7558 5.0019 10.9623 20.1637 1.5635

29.1020 54.4516 70.8244 71.5549 2.4603 4.6828 12.8585 27.4836 728.989 400.755 122.226 1.8244 31.0339 1.6812 6.8890 125.504 9.7534 290.340 32.6167 52.4394 33.8240 27.0784 38.9137 16.9881 32.8545 14.1331 1.0290 9.1837 14.3108 23.5194 13.6639 8.6864 56.0054 4.9374 4.7622 20.3089 1.6671 150.540 38.7213 34.2921 51.0549 9.2342 4.6969 50.3506 385.067 2.3595 25.8499 6.4530 1.6309

51.4689 112.400 91.8614 180.519 87.0880 51.0702 97.2062 96.9603 11.1084 55.1328 146.688 5.3600 25.2976 2.3909 3.2794 30.7818 39.9099 9.4974 43.6925 15.4910 0.8881 6.8650 3.4563 3.1451 2.7850 9.6887 0.3153 10.9773 8.3671 0.6174 0.4078 2.2053 5.0192 18.8803 1.0073 2.9791 1.1820 1.7199 5.3193 10.8988 4.9549 21.3462 0.4052 2.2894 1.5754 1.4269 2.8685 0.4209 0.8944

63.8942 317.400 136.130 152.274 100.587 61.0710 117.774 140.589 12.0205 72.821 76.425 5.9784 33.3893 27.635 2.1319 27.7756 2.5137 140.366 8.5424 22.9486 2.8489 7.6373 5.8072 1.4208 3.0296 1.0408 0.1706 20.6688 0.1496 0.6773 0.5720 1.6320 5.0856 20.9881 1.2335 1.8906 1.4933 0.5374 19.0146 3.3225 7.3723 4.9201 1.5534 4.0659 11.9521 1.6556 0.9397 3.3123 0.6703

Assignment (% TED)

NH2ass(99) NH2ss(98) m NH(96) mNH(97) mCH(93) mCH(94) mCH(95) mC10@O15(52) + mC7@O18(35) mC@O(66) mCC(65), NH2siss(33) NH2siss(64), mC@O(31) mCC(60), mC@O(28) mCC(92) mCC(91) mCC(90) mCC(51), mCN(23), bNH(19) mCC(52), mCN(30), bNH(17) mCC(46), mCN(35), bCH(16) mCN(48), mNN(39), bCH(12) mCN(42), bNH(31), bCH(26) mCN(67), bNH(33) mNN(51), bCH(32), R1asymd(13) bNH(49), bCH(33), R1symd(17) bNH(48), bCH(32), R1trigd(15) bCH (47), NH2rock(38), mCN(12) bCH(46), R1asymd(31), mCN(18) bCH(45), R1symd(30), mCN(22) NH2rock(49), R1trigd(31), xNH(18) R1asymd(45), bCO (32), xNH(19) R1symd(47), xNH(29), bCO(11) R1trigd(44), xNH(32), bCO(21) R2asymd(60), NH2wag(32) NH2wag(65), bCO(32) R2symd(69), xCH(28) R2trigd(62), xCH(29) xNH(51), R1asymd(31), xCH(13) xNH(49), R1symd(32), xCH(14) bCO(55), R1trigd(28), xCH(17) bCO(60), R2asymd(38) xCH(62), R2symd(28) xCH(63), R2trigd(33) xCH(64), tR1asymd(35) tR1asymd(72) tR1symd(71) tR1trigd(69) tR2asymd(74) tR2symd(70), xCO(28) bCN(52), tR1symd(30), xCO(12) tR2trigd(64)

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A A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A0 A00 A00 A00 A00 A00 A00 A00 A00 A00 A00 A00 A00

Observed frequencies (cm1)

0.1866 0.1656 0.0732 0.0515 0.0265

Abbreviations: m – stretching; b – in-plane bending; x – out-of-plane bending; asymd – asymmetric; symd – symmetric; t – torsion; trig – trigonal; w – weak; vw – very weak; vs – very strong; s – strong; ms – medium strong; ss – symmetric stretching; ass – asymmetric stretching; ips – in-plane stretching; ops – out-of-plane stretching; sb – symmetric bending; ipr – in-plane rocking; opr – out-of-plane rocking; opb – out-of-plane bending.

B3LYP

0.9149 1.7243 0.8168 0.5338 0.5088 1.3520 0.4967 0.7975 0.4494 0.4963

HF B3LYP HF

0.1980 0.1322 0.0837 0.0511 0.0269 303 289 274 197 177

B3LYP HF B3LYP

378 320 298 234 211 A00 A00 A00 A00 A00

234 221 166 113 93

HF FT-RAMAN

300w 285vw 271vw 198w 175w

FT7-IR

– – – – –

235 215 157 109 91

B3LYP

HF

1.6991 1.005 0.9114 8.5254 6.1292

6.2309 2.44162 1.5780 7.0904 6.8361

Assignment (% TED) Raman activity (A4/amu) IR intensity (kM/mol) Force constant (mDyne/A) Scaling frequency (cm1) Calculated frequencies (cm1) (unscaled) Observed frequencies (cm1) Symmetry species C1

Table 7 (continued)

NH2twist(52) Butterfly(61)

K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138

xCO(51), tR2trigd(32), xCN(15) xCO(66) xCN(72)

136

The theoretically computed wave number by B3LYP/6311+G(d,p) method at 3244–3195 cm1 is attributed to N–H stretching vibration. The TED also confirms that this vibration is a pure mode of contributing to 96%. The in-plane and outof-plane bending vibration of N–H group are also supported by the literature [52]. NH2 Vibrations The title molecule APH under consideration possesses NH2 group in the fourth position of the ring. The NH2 group gives rise to six internal modes of vibrations viz., the symmetric stretching, the anti symmetric stretching, the symmetric deformation or the scissoring, the rocking, the wagging and torsional modes [53]. The NH2 group has two NH stretching vibrations, one begging asymmetric and the other symmetric. The frequency of asymmetric vibration is higher than that of symmetric one. In APH the medium strong bands observed at 3352 and 3270 in the FT-IR are assigned to asymmetric and symmetric stretching vibration respectively. In the FT-Raman the very weak band at 3272 cm1 is assigned to NH2 symmetric stretching mode [54]. Based on the above conclusion, the theoretically scaled down wave number at 3354 and 3271 cm1 B3LYP/6-311+G(d,p) method are assigned to NH2 asymmetric and symmetric stretching vibrations respectively. In addition the NH2 group has scissoring, rocking, wagging and torsion modes. The deformation vibration observed in the FT-Raman spectrum as a medium strong band at 1550 cm1 is assigned to NH2 scissoring vibration. The theoretically scaled down values at 1553–1611 cm1 by B3LYP/6-311+G(d,p) methods respectively assigned to NH2 scissoring vibration. The scaled down wave number by B3LYP/ 6-311+G(d,p) method at 1067 cm1 is assigned to NH2 rocking vibration and this vibration is far below the recorded spectral range. The frequency in the FR-IR spectrum at 862 cm1 assigned to NH2 wagging mode correlates with the frequencies 864 cm1 computed by the B3LYP/6-311+G(d,p) methods respectively [55]. The NH2 twisting vibration computed by B3LYP/6-311+G(d,p) method at 197 cm1 shows good agreement with the recorded FT-Raman frequency of 175 cm1. Ring vibrations Most of the ring vibrational modes are affected by the substitutions in the ring of the title molecule. The characteristic ring stretching vibrations are assigned in the region 1650–1300 cm1 [56]. The presence of conjugate substituent such as C–C, C–N, C@O or the presence of heavy element causes a doublet formation. Therefore, the C–C stretching vibrations of APH are found at 1610, 1488, 1410, 1352, 1324 cm1 in Raman and 1492, 1430, 1382 cm1 in FTIR spectrum. The theoretically computed values for C–C vibrational modes by B3LYP/6-311+G(d,p) method (1611–1326) gives excellent agreement with experimental data. The identification of C–N stretching frequencies is a rather difficult task, since the mixing of vibrations is possible in this region. The C–N stretching vibration is usually lies in the region 1400– 1200 cm1. The C–N stretching is observed medium strong at

Table 8 Standard deviation of frequencies by HF/6-311+G(d,p) and (B3LYP)/6-311+G(d,p) basis sets. Basic set levels

Total values

Average

Standard deviation

Deviation ratio

Experimental value HF/6-311+(d,p) B3LYP/6-31+(d,p)

39,019 70,826 65,652

1500.73 1311.59 1215.77

– 99.12 93.24

– 2.60

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K. Sambathkumar et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 124–138 Table 9 Thermodynamic properties of 4-AminoPhthalhydrazide determined at different temperatures with B3LYP/6-311+G(d,p) level. T (K)

S (J/mol K)

Cp (J/mol K)

DH0 ? T (kJ/mol)

100.00 200.00 298.15 300.00 400.00 500.00 600.00 700.00 800.00 900.00 1000.00

288.02 355.75 418.63 419.78 480.36 537.12 589.89 638.81 684.15 726.29 765.57

71.28 131.32 186.14 187.10 234.88 273.85 304.83 329.51 349.45 365.86 379.56

4.75 14.87 30.51 30.85 52.02 77.53 106.53 138.29 172.27 208.06 245.35

400 350

Cp (J/mol.K)

300 250 200 150 100 50 0

200

400

600

800

1000

Temperature(K)

Fig. 11. The effect of temperature on heat capacity (Cp) of 4-AminoPhthalhydrazide. 800

700

250

200

Enthalpy change(kJ/mol)

S (J/mol.K)

600

500

400

300

200 0

200

400

600

800

150

100

50

1000

Temperature(K) 0 Fig. 10. The effect of temperature on entropy (S) of 4-AminoPhthalhydrazide.

1301 cm1 and is mixed with C–O in-plane bending vibration. This frequency is also at the lower end of the expected range which may be also due to the interaction of C–C vibration, whose frequency extends up to this value. In this study, the bands observed at FTIR 1301 cm1 and in FT-Raman 1291, 1273 cm1 of APH have been designated to C–N stretching vibrations. Also, in the present study, the bands ascribed at 980, 790 cm1 in the FTIR and bands found at 1035, 1010, 873, 821 cm1 in the Raman for the title molecule have been designated to ring in-plane bending modes by careful consideration of their quantitative descriptions. The ring out-of-plane bending modes of APH are also listed in Table 7. The reductions in the frequencies of these modes are due to the change in force constant and the vibrations of the functional groups present in the molecule. A part from these bands discussed for the title molecule there are some more absorption peaks in the observed spectra. These modes may be due to the lattice vibrations in the molecule. The lattice vibrations usually appear in the low frequency region. The low wave number hydrogen bonds expected in this region are usually weak. It is very difficult to specify exactly the appearance of any mode in this region. Some absorption peaks lying in between 400 and 150 cm1 observed in Raman spectra, which are attributed to the combinations of translational and librational motions of APH.

0

200

400

600

800

1000

Temperature(K) Fig. 12. The effect of temperature on enthalpy change (DH0 ? T) of 4AminoPhthalhydrazide.

the correlation of entropy (S), heat capacity at constant pressure (Cp) and enthalpy change (DH0 ? T) with temperature along with the correlation equations. From Table 9, one can find that the entropies, heat capacities, and enthalpy changes are increasing with temperature ranging from 100 to 1000 K due to the fact that the molecular vibrational intensities increase with temperature [57]. These observed relations of the thermodynamic functions vs. temperatures were fitted by quadratic formulas, and the corresponding fitting regression factors (R2) are all not less than 0.9995. The corresponding fitting equations for APH are

S ¼ 217:0465 þ 0:5 T  1:3609  104 T 2 C p ¼ 21:6851 þ 0:3858 T  1:5329  104 T 2

DH ¼ 4:1855 þ 0:0587 T þ 1:1077  104 T 2 Conclusion

Temperature dependence of thermodynamic properties The temperature dependence of the thermodynamic properties heat capacity at constant pressure (Cp), entropy (S) and enthalpy change (DH0 ? T) for APH were also determined by B3LYP/6311++G(d,p) method and listed in Table 9. The Figs. 10–12 depicts

In this present investigation molecular structure, vibrational frequencies, HOMO, LUMO, and polarizability analysis of APH have been studied using ab initio HF and DFT (B3LYP/6-311+G(d,p)) calculation. The NMR (1H and 13C) spectral studies are carried out at first time. Any discrepancy noted between the observed

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Further reading [40] S. Subashchandrabose, Akhil R. Krishnan, H. Saleem, V. Thanikachalam, G. Manikandan, J. Mol. Struct. 981 (2010) 59–70.